Convolutional neural networks for the automatic segmentation of lumbar paraspinal muscles in people with low back pain.

The size, shape, and composition of paraspinal muscles have been widely reported in disorders of the cervical and lumbar spine. Measures of size, shape, and composition have required time-consuming and rater-dependent manual segmentation techniques. Convolutional neural networks (CNNs) provide alternate timesaving, state-of-the-art performance measures, which could realise clinical translation. Here we trained a CNN for the automatic segmentation of lumbar paraspinal muscles and determined the impact of CNN architecture and training choices on segmentation performance. T2-weighted MRI axial images from 76 participants (46 female; age (SD): 45.6 (12.8) years) with low back pain were used to train CNN models to segment the multifidus, erector spinae, and psoas major muscles (left and right segmented separately). Using cross-validation, we compared 2D and 3D CNNs with and without data augmentation. Segmentation accuracy was compared between the models using the Sørensen-Dice index as the primary outcome measure. The effect of increasing network depth on segmentation accuracy was also investigated. Each model showed high segmentation accuracy (Sørensen-Dice index ≥ 0.885) and excellent reliability (ICC2,1 ≥ 0.941). Overall, across all muscles, 2D models performed better than 3D models (p = 0.012), and training without data augmentation outperformed training with data augmentation (p < 0.001). The 2D model trained without data augmentation demonstrated the highest average segmentation accuracy. Increasing network depth did not improve accuracy (p = 0.771). All trained CNN models demonstrated high accuracy and excellent reliability for segmenting lumbar paraspinal muscles. CNNs can be used to efficiently and accurately extract measures of paraspinal muscle health from MRI.

Imaging the lipid-phase-dependent pore formation of equinatoxin II in droplet interface bilayers.

Using phase-separated droplet interface bilayers, we observe membrane binding and pore formation of a eukaryotic cytolysin, Equinatoxin II (EqtII). EqtII activity is known to depend on the presence of sphingomyelin in the target membrane and is enhanced by lipid phase separation. By imaging the ionic flux through individual pores in vitro, we observe that EqtII pores form predominantly within the liquid-disordered phase. We observe preferential binding of labeled EqtII at liquid-ordered/liquid-disordered domain boundaries before it accumulates in the liquid-disordered phase.

Ending neglect: providing effective childhood tuberculosis training for health care workers in Tanzania.

SETTING: Health care facilities in Dar es Salaam, Pwani, and Arusha, Tanzania. OBJECTIVE: To assess health care worker (HCW) knowledge and practices 1 year after specialized training in childhood tuberculosis (TB). DESIGN: Using a standardized survey, we interviewed a convenience sample of HCWs providing both general and specialized care to children. RESULTS: We interviewed 117 HCWs in TB clinics, maternal and child health clinics, human immunodeficiency virus (HIV) clinics, out-patient departments, and pediatric in-patient wards at 12 facilities. A total of 81 HCWs (62% of nurses, 74% of clinicians) reported having attended the national childhood TB training course. Most HCWs responded correctly to questions on childhood TB diagnosis, treatment, and TB-HIV co-management, regardless of training history. Most HCWs reported that they routinely obtain chest radiographs, HIV testing, and a TB contact history when evaluating children for TB. Less than half of HCWs reported routinely obtaining sputum for mycobacterial culture or performing a tuberculin skin test. Three times as many trained as untrained HCWs reported having ever prescribed isoniazid preventive therapy (IPT) to a child (P < 0.05). CONCLUSION: In general, levels of childhood TB knowledge were high and practices were in accordance with national guidance. Specific gaps in diagnosis, treatment and use of IPT were identified for future focused training.

Contexte : Structures de soins de santé à Dar es Salam, Pwani et Arusha, Tanzanie.Objectif : Evaluer les connaissances et pratiques du personnel de santé (HCW) un an après une formation spécifique à la tuberculose de l'enfant (TB).Schéma : Grâce à une enquête standardisée, nous avons interviewé un échantillon de complaisance de HCW offrant des soins à la fois généraux et spécialisés à des enfants.Résultats : Nous avons interviewé 117 HCW dans des dispensaires de TB, des centres de santé maternelle et infantile, des dispensaires pour le virus de l'immunodéficience humaine (VIH), des consultations externes et des services de pédiatrie dans 12 établissements. Un total de 81 HCW (62% d'infirmières, 74% de cliniciens) a affirmé avoir bénéficié de la formation nationale relative à la TB de l'enfant. La majorité a répondu correctement aux questions relatives au diagnostic de la TB de l'enfant, à son traitement et à la prise en charge conjointe de la TB et du VIH, quels que soient les antécédents de formation. La plupart ont dit demander en routine des radiographies pulmonaires, un test VIH et une recherche de contacts tuberculeux lors de l'évaluation des enfants. Moins de la moitié des HCW a affirmé recueillir des crachats en routine pour une culture mycobactérienne ou réaliser un test cutané à la tuberculine. La prescription de thérapie préventive par isoniazide (IPT) a été faite trois fois plus souvent par des HCW formés que par ceux qui ne l'avaient pas été (P < 0,05).Conclusion : En général, les connaissances en matière de TB de l'enfant étaient élevées et les pratiques conformes aux directives nationales. L'étude a identifié des lacunes spécifiques en matière de diagnostic, de traitement et d'utilisation de l'IPT afin de mieux cibler les futures formations.

Marco de referencia: Los establecimientos de atención de salud de Dar es-Salaam, Pwani y Arusha en Tanzania.Objetivo: Evaluar los conocimientos y las prácticas de los profesionales de salud (HCW) un año después de haber recibido una capacitación especializada sobre la tuberculosis (TB) de la infancia.Método: Se administró una encuesta normalizada a una muestra de conveniencia de los HCW que prestan atención general y especializada a los niños.Resultados: Se entrevistaron 117 HCW de los consultorios de TB, salud maternoinfantil, atención de la infección por el virus de la inmunodeficiencia humana (VIH) y de los servicios de atención ambulatoria y hospitalización pediátrica en 12 establecimientos. Ochenta y un HCW refirieron haber asistido al programa nacional de capacitación sobre la TB en la infancia (62% del personal de enfermería y 74% del personal médico). La mayoría de los HCW respondió de manera correcta a las preguntas sobre el diagnóstico y el tratamiento de la TB y la atención integrada de la TB-VIH, independientemente de las capacitaciones recibidas. La mayoría de los interrogados refirió la solicitud sistemática de radiografías de tórax, pruebas diagnósticas del VIH y el interrogatorio sobre los antecedentes de contacto con casos de TB cuando examinaba niños con presunción clínica de TB. Menos de la mitad de los HCW declaró la obtención corriente de muestras de esputo para cultivo de micobacterias o la práctica de la prueba cutánea de la tuberculina. Fue tres veces más frecuente que los HCW que habían recibido una capacitación, hubiesen recetado en alguna ocasión el tratamiento preventivo con isoniazida (IPT) a un niño en comparación con HCW sin antecedentes de capacitación (P < 0,05).Conclusión: En general, se observó un buen conocimiento de la TB de la infancia y las prácticas fueron conformes con las directrices nacionales. Se pusieron en evidencia algunas deficiencias en materia de diagnóstico, tratamiento y aplicación del IPT, sobre las cuales se centrará la atención en los futuros programas de capacitación.

A comparison of induced astigmatism in 20- vs 25-gauge vitrectomy procedures.

INTRODUCTION: Surgically induced astigmatism is an unwanted variable that can lead to poorer visual and refractive outcomes in patients undergoing vitrectomy even when a technically precise procedure has been performed. This study assesses the difference in surgically induced astigmatism (SIA) between the traditional 20-gauge vitrectomy and the newer 25-gauge sutureless technique by comparing pre- and post-procedure keratometry readings. METHOD: The study is a retrospective consecutive case series of vitrectomies performed by a single surgeon. There were a total of 47 patients, eight with bilateral procedures, 24 who underwent the 20 gauge, and 31 who had the 25-gauge procedure. Patients were excluded for corneal altering pathology or scleral buckling procedures. Vector analysis of pre- and post-vitrectomy readings was performed using Alpin's method, facilitated by the ASSORT program version 4.1. RESULTS: Mean time at which post-operative keratometry readings were taken was 3.9 months (1-36). Mean astigmatism at presentation was 0.63 D and 0.92 D and at post-surgically follow-up 1.14 D and 0.91 D (20 and 25 gauge, respectively). Mean SIA was 0.66 D (SD=0.8 D) for the 20-gauge group and 0.27 D (SD=0.23 D) for the 25 gauge (P=0.037). The calculated figure of SIA variability representing the 95% CI for the maximum amount of SIA for each procedure was 2.26 D and 0.73 D for the 20- and 25-gauge procedure, respectively. CONCLUSIONS: The study shows that the 25-gauge technique involves a statistically significant reduction in the amount of SIA. This can ultimately lead to a better visual and refractive outcome for the patient.

An inconvenient truth about thermoelectrics.

Despite recent advances, thermoelectric energy conversion will never be as efficient as steam engines. That means thermoelectrics will remain limited to applications served poorly or not at all by existing technology. Bad news for thermoelectricians, but the climate crisis requires that we face bad news head on.

Onset of submarine debris flow deposition far from original giant landslide.

Submarine landslides can generate sediment-laden flows whose scale is impressive. Individual flow deposits have been mapped that extend for 1,500 km offshore from northwest Africa. These are the longest run-out sediment density flow deposits yet documented on Earth. This contribution analyses one of these deposits, which contains ten times the mass of sediment transported annually by all of the world's rivers. Understanding how this type of submarine flow evolves is a significant problem, because they are extremely difficult to monitor directly. Previous work has shown how progressive disintegration of landslide blocks can generate debris flow, the deposit of which extends downslope from the original landslide. We provide evidence that submarine flows can produce giant debris flow deposits that start several hundred kilometres from the original landslide, encased within deposits of a more dilute flow type called turbidity current. Very little sediment was deposited across the intervening large expanse of sea floor, where the flow was locally very erosive. Sediment deposition was finally triggered by a remarkably small but abrupt decrease in sea-floor gradient from 0.05 degrees to 0.01 degrees. This debris flow was probably generated by flow transformation from the decelerating turbidity current. The alternative is that non-channelized debris flow left almost no trace of its passage across one hundred kilometres of flat (0.2 degrees to 0.05 degrees) sea floor. Our work shows that initially well-mixed and highly erosive submarine flows can produce extensive debris flow deposits beyond subtle slope breaks located far out in the deep ocean.

Photofragment slice imaging studies of pyrrole and the Xe...pyrrole cluster.

The photolysis of pyrrole has been studied in a molecular beam at wavelengths of 250, 240, and 193.3 nm, using two different carrier gases, He and Xe. A broad bimodal distribution of H-atom fragment velocities has been observed at all wavelengths. Near threshold at both 240 and 250 nm, sharp features have been observed in the fast part of the H-atom distribution. Under appropriate molecular beam conditions, the entire H-atom loss signal from the photolysis of pyrrole at both 240 and 250 nm (including the sharp features) disappear when using Xe as opposed to He as the carrier gas. We attribute this phenomenon to cluster formation between Xe and pyrrole, and this assumption is supported by the observation of resonance enhanced multiphoton ionization spectra for the (Xe...pyrrole) cluster followed by photofragmentation of the nascent cation cluster. Ab initio calculations are presented for the ground states of the neutral and cationic (Xe...pyrrole) clusters as a means of understanding their structural and energetic properties.

The role of pisigma* excited states in the photodissociation of heteroaromatic molecules.

High-resolution measurements of the kinetic energies of hydrogen atom fragments formed during ultraviolet photolysis of imidazole, pyrrole, and phenol in the gas phase confirm that N(O)-H bond fission is an important nonradiative decay process from their respective 1pisigma* excited states. The measurements also reveal that the respective cofragments (imidazolyl, pyrrolyl, and phenoxyl) are formed in very limited subsets of their available vibrational states. Identification of these product states yields uniquely detailed insights into the vibronic couplings involved in the photoinduced evolution from parent molecule to ultimate fragments.

High resolution photofragment translational spectroscopy of the near UV photolysis of indole: dissociation via the 1pi sigma* state.

The fragmentation dynamics of indole molecules following excitation at 193.3 nm, and at a number of different wavelengths in the range 240 < or = lambda(phot) < or = 286 nm, have been investigated by H Rydberg atom photofragment translational spectroscopy. The longer wavelength measurements have been complemented by measurements of excitation spectra for forming parent and fragment ions by two (or more) photon ionisation processes. Analysis identifies at least three distinct contributions to the observed H atom yield, two of which are attributable to dissociation of indole following radiationless transfer from the 1pi pi* excited states (traditionally labelled 1L(b) and 1L(a)) prepared by UV single photon absorption. The structured channel evident in total kinetic energy release (TKER) spectra recorded at lambda(phot) < or = 263 nm is rationalised in terms of N-H bond fission following initial pi* <-- pi excitation and subsequent coupling to the 1pi sigma* potential energy surface via a conical intersection between the respective surfaces--thereby validating recent theoretical predictions regarding the importance of this process (Sobolewski et al., Phys. Chem. Chem. Phys., 2002, 4, 1093). Analysis provides an upper limit for the N-H bond strength in indole: D0(H-indolyl) < or = 31,900 cm(-1). Unimolecular decay of highly vibrationally excited ground state molecules formed by internal conversion from the initially prepared 1pi pi* states is a source of (slow) H atoms but their contribution to the TKER spectra measured in the present work is dwarfed by that from H atoms generated by one or more (unintended but unavoidable) multiphoton processes.

Quantification of skeletal kinetic indices in Paget's disease using dynamic 18F-fluoride positron emission tomography.

The purpose of this study was to quantify indices of regional bone metabolism in Paget's disease and to compare these indices with normal bone using dynamic 18F-fluoride positron emission tomography (PET). Seven patients with vertebral Paget's disease had 1 h dynamic 18F-fluoride PET scans performed. The scans included a diseased vertebra and an adjacent normal vertebra. Arterial plasma input functions were also measured. A three-compartment, four-parameter model was used with nonlinear regression analysis to estimate bone kinetic variables. Compared with normal bone, pagetic bone demonstrated higher values of plasma clearance to bone mineral (Ki; 1.03 x 10(-1) vs. 0.36 x 10(-1) ml/min per milliliter; p = 0.018) and clearance to total bone tissue (K1; 2.38 x 10(-1) vs. 1.25 x 10(-1) ml/min per milliliter; p = 0.018), reflecting increased mineralization and blood flow, respectively. Release of 18F-fluoride from bone mineral (k4) was lower in pagetic bone (p = 0.022), suggesting tighter binding of 18F-fluoride to bone mineral. The notional volume of the extravascular bone compartment (K1/k2) was greater in pagetic bone (p = 0.018). Although the unidirectional extraction efficiency from the extravascular space to bone mineral (Ki/K1) was greater in pagetic bone (p = 0.018), a lower pagetic value of k2 (p = 0.028), describing the rate of transfer from the bone extravascular compartment to plasma, suggests that the 18F-fluoride that enters the relatively fibrotic marrow space of pagetic bone may be less accessible for return to plasma. These findings confirm some of the known pathophysiology of Paget's disease, introduce some new observations, and show how dynamic 18F-fluoride PET may be of value in the measurement of regional metabolic parameters in focal bone disorders.

Effect of corrections for blood glucose and body size on [18F]FDG PET standardised uptake values in lung cancer.

Standardised uptake values (SUVs) are commonly used as a semi-quantitative index of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) tracer uptake in positron emission tomography (PET). Studies have shown that SUVs may depend on body size and blood glucose concentration and corrections for these effects have been proposed in the literature. This retrospective study investigated the effect of the proposed corrections on SUVs from a group of 154 patients with lung cancer who had scans on a dedicated PET scanner. A total of 252 SUVs were requested as an aid to staging during consideration for surgical resection. SUVs were calculated normalised to body weight (SUVw), lean body mass (SUV(LBM)) and body surface area (SUV(BSA)). The following correlations were examined: SUV with height, weight and body surface area for the different body size normalisations; SUVw and SUVw x blood glucose (SUV(BG)) with blood glucose; SUVw with scan time post injection; and SUVw with apparent lesion diameter. Significant correlations were only observed between: SUV(LBM) and height (P=0.007); SUVw and scan time (P=0.007); SUVw and lesion diameter (P=0.0005); and SUV(BG) and blood glucose (P<0.00001). The correlation between SUV(LBM) and height suggests that lean body mass as a function of height alone should not be used to normalise SUVs; however, the lean body mass calculated from a height and weight nomogram did not show this effect. The strong correlation between SUV(BG) and blood glucose concentration suggests that for non-diabetic fasted patients, lung tumour SUVs should not be adjusted for blood glucose.

Radiation dose rates from patients undergoing PET: implications for technologists and waiting areas.

Increasingly hospitals are showing an interest in developing their imaging services to include positron emission tomography (PET). There is therefore a need to be aware of the radiation doses to critical groups. To assess the effective whole-body dose received by technologists within our dedicated PET centre, each staff member was issued with a dose rate meter, and was instructed to record the time spent in contact with any radioactive source, the dose received per working day and the daily injected activity. On average each technologist administered 831 MBq per day. The mean whole-body dose per MBq injected was 0.02 microSv/MBq(-1). The average time of close contact (<2.0 m) with a radioactive source per day was 32 min. The average effective dose per minute close contact was 0.5 microSv/min(-1), which resulted in a mean daily effective dose of 14.4 microSv. No technologist received greater than 60 microSv (the current UK limit for non-classified workers) in any one day, and in general doses received were less than 24 microSv, the daily dose corresponding to the proposed new annual limit for non-classified workers of 6.0 mSv per annum. However, we recognise that the layout of nuclear medicine departments will not mirror our own. We therefore measured the instantaneous dose rates at 0.1, 0.5, 1.0 and 2.0 m from the mid-thorax on 115 patients immediately after injection, to provide estimates of the likely effective doses that might be received by technologists operating dual-headed coincidence detection systems, and others coming into contact in the waiting room with patients who have been injected with fluorine-18 fluorodeoxyglucose. The mean (95th percentile) dose rates measured at the four aforementioned distances were 391.7 (549.5), 127.0 (199.8), 45.3 (70.0) and 17.1 (30.0) microSv/h(-1), respectively. A number of situations have been modelled showing that, with correct planning, FDG studies should not significantly increase the effective doses to technologists. However, one possible area of concern is that, depending on the number of patients in a waiting area at any one time, accompanying persons may approach the limits set by the new UK IRR 1999 regulations for members of the public.

Evaluation of myocardial perfusion using positron emission tomography in infants following a neonatal arterial switch operation.

This study was performed to examine the use of positron emission tomography (PET) as a method of evaluating myocardial perfusion after the arterial switch operation for correction of transposition of the great arteries. Eleven asymptomatic patients (median age 2.3 years, range 1.3-4.3 years) post successful neonatal arterial switch repair for transposition underwent cardiac PET scanning using N(13) ammonia before and after dipyridamole infusion. Reconstructed data from static scans were analyzed for regional perfusion defects before and after pharmacological stress. Simultaneous assessment of coronary flow before and after stress was performed using a Patlak graphical analysis of data from dynamic scans. Results obtained from PET scanning were correlated with patterns of coronary artery anatomy, electrocardiogram (ECG) recordings, and echocardiographic evaluation. PET scanning demonstrated normal distribution of myocardial perfusion before and after stress in all but one patient, who was found to have a discrete inferior transmural perfusion defect. The defect was well correlated with perioperative ECG changes and a complicated postoperative course. Myocardial blood flow before dipyridamole (0.690 ml/min/g) was similar to reported adult rest values. There was a small but significant (p < 0.002) increase in myocardial blood flow after dipyridamole stress with a mean coronary flow reserve of 1.19 (+/-0.103). Echocardiographic evaluation failed to demonstrate significant wall motion abnormalities in any of the patients. Cardiac PET scanning is a reliable noninvasive method for evaluation of myocardial perfusion in small children. In this study, the incidence of myocardial perfusion defects after the arterial switch operation is lower than previously reported. The data obtained concerning coronary flow and coronary flow reserve after the arterial switch need to be interpreted with caution because normal data in children are not available.

Evaluation of (18)fluorodeoxyglucose positron emission tomography ((18)FDG PET) in the detection of malignant peripheral nerve sheath tumours arising from within plexiform neurofibromas in neurofibromatosis 1.

OBJECTIVES: The ability of (18)fluorodeoxyglucose positron emission tomography ((18)FDG PET) to detect malignant change in plexiform neurofibromas from patients with neurofibromatosis 1 (NF1) was evaluated. METHODS: Eighteen NF1 patients who presented with pain, increase in size, or neurological deficit associated with a plexiform neurofibroma were assessed. Magnetic resonance imaging determined the site and extent of the lesion. Qualitative(18)FDG PET was performed and the standard uptake value (SUV) measured the regional glucose metabolism. Histological confirmation of the diagnosis was obtained in 10 patients. RESULTS: Twenty three plexiform neurofibromas were detected in 18 patients. Seven malignant peripheral nerve sheath tumours, four high grade and three low grade tumours, occurred in five patients. In one patient the clinical and radiological characteristics of the tumour suggested malignancy, but histology was inconclusive. Fifteen benign plexiform neurofibromas were identified in 12 patients and these findings were confirmed histologically in five lesions from four patients. Ten plexiform neurofibromas occurring in eight patients were considered benign on(18)FDG PET and the patients did not undergo surgery. They remained stable or their symptoms improved on clinical follow up (median 9 months). The results of qualitative (18)FDG PET were interpreted as indicating that 13 plexiform neurofibromas were benign and 10 were malignant. No malignant tumours were classified as benign, but two benign tumours were reported as malignant. The SUV was calculated for 20 tumours and was significantly higher in five malignant tumours 5.4 (SD 2.4), than in 15 benign tumours 1.54 (SD 0.7), p=0.002. There was an overlap between benign and malignant tumours in the SUV range 2.7-3.3. CONCLUSIONS: (18)FDG PET is helpful in determining malignant change in plexiform neurofibromas in NF1. Increased separation between benign and malignant lesions could be obtained by calculating the SUV at about 200 minutes after injection of (18)FDG, when the peak activity concentration is obtained in malignant tumours.

Prospective evaluation of soft tissue masses and sarcomas using fluorodeoxyglucose positron emission tomography.

BACKGROUND: The differentiation of soft tissue sarcoma (STS) from benign masses is difficult owing to their clinical and radiological similarities. Accurate staging is hindered by the large number of sites at which metastases may be found. This study examined the value of whole-body [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) in patients presenting with soft tissue masses. METHODS: Thirty patients with a soft tissue mass suspected to be malignant were evaluated with FDG PET. The images were evaluated qualitatively and quantitatively for uptake of FDG to determine whether benign lesions could be differentiated from malignant tumours, and for the presence of metastases. RESULTS: Thirty-one masses were removed from 30 patients; 12 were benign and 19 were malignant STSs. Using qualitative assessment of the FDG PET images, all the high-grade STSs (n = 12) were correctly identified, but low-grade STS (n = 7) could not be differentiated from a benign lesion. Using a quantification assessment, there was a 95 per cent sensitivity and a 75 per cent specificity in diagnosing STS. Three patients had metastases at presentation; two were correctly identified by FDG PET. CONCLUSION: FDG PET has a role in distinguishing high-grade STS from low-grade or benign STS and may have a role in staging malignant tumours.

Are restrictions to behaviour of patients required following fluorine-18 fluorodeoxyglucose positron emission tomographic studies?

The clinical use of positron emission tomography (PET) is expanding rapidly in most European countries. It is likely therefore that patients receiving the tracer fluorine-18 fluorodeoxyglucose (18FDG) will be discharged to come into contact with family members, members of the public and ward staff. There are few direct measurements on which to base any recommendations with regard to radiation protection, and so we have measured the dose rates from patients undergoing clinical PET examinations in our centre. Seventy-five patients who underwent whole-body and brain 18FDG PET examinations were studied. Dose rates were measured at 0.1, 0.5, 1.0 and 2.0 m from the mid thorax on leaving the department. The median administered activity was 323 MBq with a 95th percentile value of 360 MBq. The median dose rates measured at the four distances were 90.0, 35.0, 14.0 and 5.0 microSv h-1 (the median dose rates per unit administered activity at 2 h post injection were 0.31, 0.11, 0.04 and 0.02 microSv h-1 MBq-1). The corresponding 95th percentile values were 174.0, 69.0, 29.0 and 7.5 microSv h-1 (0.43, 0.2, 0.08 and 0.03 microSv h-1 MBq-1). A number of social situations were modelled and an annual dose limit of 1 mSv was used to determine whether restrictive behavioural advice was required. In the case of nursing staff on wards a value of 6 mSv was regarded as the annual limit, which translates to a daily limit of approximately 24 microSv. There is no need for restrictive advice for patients travelling by public or private transport when they leave the department 2 h after the administration of 18FDG. Similarly, there is no need for restrictive advice with regard to their contact with partners, work colleagues or children of any age, although it should be stressed that children should not accompany the patient to the scanning department. The only possible area of concern is in an oncology ward, where patients may be regularly referred for PET investigations and other high activity radionuclide studies and are partially helpless. Even in this area, however, it is unlikely that a nurse would receive a daily dose of more than 24 microSv. We conclude that there is no need for restrictive advice for patients undergoing 18FDG PET studies given the current administered activities.